This invention refers to a jet for the carburetor of a gasoline internal combustion engine, including means for the automatically correcting the composition (dosing) of the mixture which is delivered in the different operation conditions of the engine.
As known, an elementary carburetor, comprising a choke in the form of a venturi tube where the air sucked by the engine flows, a gasoline jet located in the restricted cross section of the choke, a constant level fuel bowl which feeds the gasoline to the jet, and a calibrated nozzle (fuel nozzle) located between the fuel bowl and the jet, supplies to the engine an air and gasoline mixture whose composition is not constant but changes with the increase of the air flow sucked by the engine. Different devices have been proposed in order to automatically correct this change in the composition of the delivered mixture. Among them it is often used a so called air brake device, which includes a sump located between the fuel nozzle and the jet. A blind tube having an apertured wall plunges within the sump and at top it communicates with the ambient air through another calibrated nozzle (air nozzle). Thanks to this device the jet sucks, along with the gasoline which flows through the fuel nozzle, some air which is sucked through the air nozzle and comes out through the apertures in the tube wall. This air opposes some resistance to the gasoline flow within the sump, and this resistance increases when the flow increases, whereby the desired correction may be obtained within certain limits during a constant speed operation. However such device has some drawbacks. It considerably complicates the carburetor structure; its manufacture is somewhat expensive; the setup thereof is difficult and does not allow to obtain a complete correction; and the access to its component parts is difficult even for the simple cleaning. This device has a favorable action during the operation with varying speed too, namely during the acceleration, because the tube which plunges within the sump contains a gasoline reserve, which may be rather easily sucked since it is not hindered by the fuel nozzle but only by the apertures in the tube wall. This action, however, is not practically sufficient, whereby in most cases it is needed that an accelerator pump is provided for.